Study: Back-to-back hurricanes more likely
What used to be a rare one-two punch of consecutive hurricanes hitting about the same place in the United States weeks apart seems to be happening more often, and a recent study says climate change will make back-to-back storms more frequent and nastier in the future.
Separately, another report released last month showed hurricane winds fueled by climate change will reach further inland and put tens of millions more Americans’ lives and homes at risk in the next three decades, according to data from the nonprofit First Street Foundation.
Using computer simulations, scientists at Princeton University calculate that the deadly storm duet that used to happen once every few decades could happen every two or three years as the world warms from the burning of coal, oil and natural gas, according to a study in Nature Climate Change.
Louisiana and Florida residents have already felt it.
In 2021, major Hurricane Ida blasted Louisiana with 150 mph winds. Just 15 days later a weakening Nicholas came nearby, close enough for its wind, rain and storm surge to add to the problems, said study co-author Ning Lin, a risk engineer and climate scientist at Princeton. Her study looked at not just the storms but the problems back-to-back hurricanes caused to people.
The Ida-Nicholas combo came after Louisiana was hit in 2020 by five hurricanes or tropical storms: Cristobal, Marco, Laura, Delta and Zeta.
After Laura, relief workers had set up a giant recovery center in a parking lot of a damaged roofless
church when Delta approached, so all the supplies had to be jammed against the building and battened down for the next storm, said United Way of Southwest Louisiana President Denise Durel.
“You can’t imagine. You’re dumbfounded. You think it can’t be happening to us again,” Durel recalled 2 ½ years later from an area that is still recovering. “The other side of it is that you can’t wish it upon anyone else either.”
Florida in 2004 had four hurricanes in six weeks, prompting the National Oceanic Atmospheric Administration to take note of a new nickname for the Sunshine State — “The Plywood State,” from all the boarded-up homes.
“We found a trend,” Lin said. “Those things are happening. They’re happening more often now than before.”
There’s a caveat to that trend. There haven’t been enough hurricanes and tropical storms since about 1950 — when good recordkeeping started — for a statistically significant
trend, Lin said. So her team added computer simulations to see if they could establish such a trend and they did.
Lin’s team looked at nine U.S. storm-prone areas and found an increase in storm hazards for seven of them since 1949. Only Charleston, S. C., and Pensacola, Fla., didn’t see hazards increase.
The team then looked at what would happen in the future using a worst-case scenario of increasing carbon dioxide emissions and a more moderate scenario in line with current efforts worldwide to reduce greenhouse gases. In both situations, the frequency of back-to-back storms increased dramatically from current expectations.
The reason isn’t storm paths or anything like that. It’s based on storms getting wetter and stronger from climate change as numerous studies predict, along with sea levels rising. The study looked heavily at the impacts of storms more than just the storms themselves.
“For people in harm’s
way this is very bad news,” University of Albany hurricane scientist Kristen Corbosiero, who wasn’t part of the study, said in an email. “We (scientists) have been warning about the increase in heavy rain and significant storm surges with landfalling TCs (tropical cyclones) in a warming climate and the results of this study show this is the case.”
Corbosiero and four other hurricane experts who weren’t part of the study said it made sense. Some, including Corbosiero, say it is hard to say for sure that the back-to-back trend is already happening.
In the other report, the First Street Foundation, a nonprofit that works to define and communicate risks posed by climate change, says it has developed a model to assess “hyperlocal climate wind risk” now and into the future.
A Washington Post analysis of the group’s data found that nearly 30 million Americans in about 235 counties across 18 states in the contiguous United States, from Texas to New England, will face new threats from hurricane-force winds.
Because of changes in weather patterns due to climate change, these storms would also be able to sustain themselves long enough to travel farther. A third of Americans could experience damaging gales by 2053, in places as far inland as Illinois, Tennessee and Arkansas.
The group based its model on pioneering peerreviewed research by Kerry Emanuel, an atmospheric scientist at the Massachusetts Institute of Technology. Emanuel projected in 2006 that climate change was likely to increase storms’ intensity and might shift their geography.
Working with Emanuel on the new study, researchers simulated 50,000-plus storm tracks based on warming climate conditions. In the future, they determined, more storms in the U.S. would likely reach a strength of Category 3 or higher.
“The physics just allow for the formation of more intense storms,” said Matthew Eby, First Street’s founder and chief executive. “There’s a big jump in who might be facing the most extreme end of the spectrum.”
According to the First Street analysis, there are about 3.5 million properties within the contiguous United States with any chance of experiencing Category 5 hurricane winds.
In 30 years, that number will increase to more than 5.6 million.
And people continue to move to possibly problematic areas. The Post analysis found people have been moving to counties categorized as high risk for hurricane-force winds at six times the rate of other counties.
“Even if the risks are well known, it doesn’t mean, unfortunately, that we are going to be well prepared,” Emanuel said.
More hurricanes are likely to track northward over coming years, due to a range of factors, including moisture levels in the atmosphere and changing large-scale wind patterns. As the tropical regions that help to fuel hurricanes expand toward the poles in a warming planet, so do the range of the storms themselves.
“The storms are just living in their world, and their world is growing,” said James Kossin, a retired National Oceanic and Atmospheric Administration atmospheric scientist, who has studied hurricanes but did not work on Monday’s analysis.
Florida is and will remain the U.S. state most exposed to hurricane risk, according to First Street. The top 20 cities in danger of encountering a major hurricane in the next decades are all in Florida.
The Gulf Coast will continue to experience the strongest winds, with maximum gusts of about 248 miles per hour. South Carolina is expected to see the largest increase in maximum wind speeds over the next 30 years, with top winds 37 mph higher than now.
Ed Kearns, chief data officer for First Street, said a key part of preparing for these changes is arming people with information about what is coming.
“The risk is shifting. That’s what we are trying to impart,” he said. “Risk is most dangerous when you don’t know you have it.”